THE FACE

And the last thing, don't you think the face of Wahington is a little bit clenched? Because he had a false teeth. This painting shows a natural expression of Washington.

Stuart wrote that:

When I painted him [Washington], he had just had a set of false teeth inserted, which accounts for the constrained expression so noticeable about the mouth and lower part of the face...Houdon's bust does not suffer from this defect."

info came from wikipedia.